Separation of mixtures of hydrocarbons



Patented July 27, 1937 UNITED STATES PATENT OFFICE SEPARATION OFMIXTURES F H pno- CARBONS No Drawing. Application May 21, 1936,

Serial No. 81,019

6 Claims. (Cl. 196-13) This invention relates to the separation ofmixtures of hydrocarbons by selective solvent action and moreparticularly to the solvent refining of mineral oils.

It is now well known that a large proportion of the mineral oils andgasolines of today are complex mixtures of parafiinic and non-paraffinichydrocarbons. It is frequently desirable to separate the non-paraifinichydrocarbons from the paraifinic hydrocarbons for various reasons. Oneof the main reasons is that the parafiinic hydrocarbons are in generalmore resistant to decomposition through heat and oxidation than thenon-paraflinic hydrocarbons. Accordingly, the oil containing the largerproportion of paraffinic constituents or, in other words, the relativelymore parafilnic oils are more stable than the less paraflinic oils andhence are more desirable as lubricants and for other purposes.

Various methods have been proposed for separating the non-paraflinicfrom the parafiinic constituents of oils. One of the more common andoldest is by treatment with sulfuric acid which removes some of thenon-paraflinic compounds from the oils. More recently it has beenproposed to separate the non-parafiinic hydrocarbons by means ofselective solvent'extraction.

An object of the present invention is to provide a method for separatinga mixture of paraffinic and non-parafiinic hydrocarbons into portions,one of which is relatively more paraflinic than the original mixture andthe other relatively less parafiinic. Another object is the separationof relatively non-paraifinic bodies from mineral lubricating oils toproduce lubricating oils of relatively high paraflinic character. Afurther object is the production of lubricating oils with improvedviscosity-temperature curves from oils with poor viscosity-temperaturecurves. A still further object is to provide oils with improvedresistance to oxidation and decomposition and to advance the art. Stillother objects will appear hereinafter.

These objects may be accomplished in accordance with my invention bymixing mixtures of parafiinic and non-parafiinic hydrocarbons withfurfurylamine (C4H3OCH2N'H2) to remove the non-paraflinic hydrocarbonsby the selective solvent action of the furfurylamine. The oil is mixedwith the furfurylamine under such conditions that two layers are formed,one of which comprises the constituents which it is desired to extractfrom the oil, dissolved in the bulk of the solvent liquid, while theother comprises the 5 undissolved and relatively parafiinic oil inadmixture with a solvent.

1 Preferably, my method comprises mixing the furfurylamine with thehydrocarbon mixture in approximately equal volumes and heating with 5agitation to a temperature at which the solvent and oil becomecompletely miscible. This solution is then cooled with agitation to atemperature approximately. 20 0. below the temperature of completemiscibility, allowing the mixture to stand until separation into twolayers occurs, sep arating the layers and removing the 'furfurylaminefrom each layer. The furfurylamine may be separated from thehydrocarbons by distillation. The residue, from the layer containing thelarger amount of solvent, consists of a large proportion ofnon-paraffinic and undesirable constituents. The residue, from the layercontaining the smaller amount of solvent, consists primarily of thedesirable paraffinic hydrocarbons.

In the examples given below, the selective removal of non-paracfiinicconstituents from a mineral oil has been measured by following thechange in the viscosity-gravity constant of the oil. This constant hasbeen described by J. B. Hill and H. B. Coates in Industrial andEngineering Chemistry,volume 20, page 641 et seq., in an articleentitled The viscosity-gravity constant of petroleum lubricating oils.--If a given crude petroleum be distilled into successive fractions andthe specific gravities and viscosities of the several fractionsdeterminecLlit will be found that they conform to the generalrelationship:

1.0752-a log (V-38) in which G is the specific gravity at F., V isSaybolt universal viscosity at 100 F. and a is the viscosity-gravityconstant. These constants are lower for fractions of paraflinic crudesthan are the constants for fractions of the nonrelatively small amountof the paraffinic crudes'; The viscosity-gravity constant is, therefore,an index of the paraflinicity of an oil and a decrease in the value ofthis constant for a given fraction of lubricating oil indicates anincrease in paraffin hydrocarbon content.

Example 1 A lubricating oil distillate (with the followingcharacteristics: viscosity at 100 F., 566 sec. Saybolt universal;specific gravity at 60 F./60 F., 0.927; viscosity-gravity constant,0.872) was mixed with an equal volume of furfurylamine and heated withagitation to C. at which temperature solvent and oil were miscible. The

solution was cooled to 40 C. while agitating, allowed to settle one-halfhour, and the two layers withdrawn into separate containers.Furiurylamine was removed from both layers under reduced pressure.Eighty percent (80%) of the original oil volume was found in the toplayer and had a viscosity-gravity constant of 0.856 as compared to 0.872for the original oil.

Example 2 A portion of the same crude lubricating oil distillateemployed in Example 1 was heated with one and one-half times its volumeof furfurylamine to 50 C. with agitation, cooled to 30 C. withagitation, and allowed to stand one-half hour. The two layers whichformed were treated as in Example 1, with anoil recovery in the toplayer of 74%. This treated oil had a viscositygravity constant of 0.850as compared to 0.872 for the original oil.

The above examples are merely illustrative of my invention. It will bereadily apparent that other oils may be treated in a like manner toproduce similar results. Also, in certain cases N-substitutedfurfurylamines such as methyl furiurylamine and the like, may besubstituted for the furfurylamine. Further, it is not necessary for thefurfurylamine to be pure but it may be employed in a mixture withothercompounds and particularly with other selective solvents.

The conditions of application of the solvent will vary with the natureof the oil. Highly naphthenic oils will, in general, require a lowertemperature to effect separation than highly paraffinic oils. Thetemperatures employed will, in general, range from about C. to about 200C. At the higher temperatures, it may be necessary to employ pressure toprevent substantial vaporization of the solvent. The ratio of solvent tooil may be varied within rather wide limits and will depend largely uponthe nature of the oil being treated, the amount of :non-parafilnicconstituents therein and the quality of the refined oil desired. Ingeneral, the ratio of solvent to oil will lie between 1 to and 5 to 1parts by volume.

While distillation is the preferred method for separating the solventfrom the oil, other means may be employed such as conversion of theamine solvent into an insoluble salt or extraction of the amine with asolvent which is a non solvent for the oil. My process may be applied toa raw distillate or to a partially refined product, or to crackedgasolines, cracked naphtha and the like. Under certain conditions, asfor example in the case of oils with high sulphur content or poorsludging characteristics, it may be desirable to supplement theextractiontreatment with the usual acid, alkali, doctor or claytreatment, applied either before or after the solvent extraction.

While I have disclosed the preferred embodiments of 1myinvention and thepreferred modes of carrying the same into efiect, it will be readilyapparent to those skilled in the art that many variations andmodifications may be made therein without departing from the spirit ofmy invention. Accordingly, the scope of my invention is to be limitedsolely by the appended claims construed as broadly as is permissible inview of the prior art.

I claim:

1. The method of treating a normally liquid hydrocarbon mixturecontaining relatively parailmic and relatively non-parafiinic compoundswhich comprises extracting the hydrocarbon mixture with a furfurylamineto separate the relatively non-paraflinic compounds from the relativelyparaffinic. compounds.

2. The method of treating a normally liquid hydrocarbon mixturecontaining relatively paraifinic and relatively non-paraflinic compoundswhich comprises mixing a furfurylamine with the hydrocarbon mixture,causing the resulting mixture to separate into two layers and separatingthe layers, whereby the relatively non-parafiinic compounds areseparated from the relatively paraffinic compounds. i

3. The method of treating a normally liquid hydrocarbon mixturecontaining relatively paraflinic and relatively non-parafiinic compoundswhich comprises mixing a furfurylamine with'the hydrocarbon mixture,heating the resulting mixture to a temperature where the furfurylaminebecomes completely miscible with the hydrocarbon mixture, cooling toabout 20 C. below the temperature of complete miscibility and causingthe mixture to separate into two layers, separating the two layers, 'andremoving the furfurylamine from each layer, whereby the relativelynon-parafiinic compounds are separated from the relatively parafliniccompounds. 1

4. The method of treating a normally liquid hydrocarbon mixturecontaining relatively paraflinic and relatively non-paraflinic compoundswhichcomprises extracting the hydrocarbon mixture with furfurylamine toseparate the relatively non-paraflinic compounds from the relativelypararfinic compounds.

5. The method of treating a normally liquid hydrocarbon mixturecontaining relatively paraffinic and relatively non-parafiinic compoundswhich comprises mixing furfurylamine with the hydrocarbon mixture,causing the resulting mixture to separate into two layers and separatingthe layers, whereby the relatively non-paraffinic compounds areseparated from'the relatively paraflinic compounds.

6. The method of treating a normally liquid hydrocarbon mixturecontaining relatively paraffinic and relatively non-paraflinic compoundswhich comprises mixing furfurylamine with the hydrocarbon mixture,heating the resulting mixture to a temperature where the furfurylaminebecomes completely miscible with the hydrocarbon mixture, cooling toabout 20 C. below the temperature of complete miscibility and causingthe mixture to separate into two layers, separating. the two layers, andremoving the furfurylamine from each layer, whereby the relativelynon-paraifinic compounds are separated from the relatively parafiiniccompounds.

PAUL L. SALZBERG.

